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TU Berlin

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Project A.4: The interplay of coherence and Brownian motion for excitation transfer in colloidal quantum dots

In this project, we will analyze the combined THz/optical response of excitation transfer between (i) bright and dark states in individual CdSe-QDs and (ii) different CdSe-QDs exhibiting Brownian motion. Whereas the internal charge transfer results in emission intermittency, the Brownian motion has impact on the formation of collective states due to dipole excitation exchange between different QDs. We aim to theoretically identify unique signatures of these processes in coherent nonlinear optical spectroscopy to clarify the:
(i) contributions to the intermittency (trapped states, tunneling, electron leaking), (ii) interplay of Brownian motion (position, orientation of QDs) and dipole coupling between different dots.
The spectroscopic signals to be analyzed include absorption-, excited state- and two dimensional spectroscopy. In particular, specific methods are sensitive to near field dipole-dipole interactions and detect configurations for particle sizes below the diffraction limit complementary to scattering experiments. Also Coulomb Green’s functions with boundary conditions are used to account for surface charges in solvent and ligands. The motion of the QDs is addressed using Brownian dynamic simulations.

Project leaders: Prof. Dr. A. Knorr, Prof. Dr. H. Stark

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